Testing Robustness of WMAP Temperature Calibration to Timing Offsets

Abstract

Results derived from data obtained by Wilkinson Microwave Anisotropy Probe (WMAP) are extensively used in many areas of physics. It has been claimed recently that the published WMAP calibrated data and maps might be in question because of an undocumented timing offset in the official processing pipeline [The origin of the WMAP quadrupole, Hao Liu, Shao-Lin Xiong, Ti-Pei Li]. This timing error was shown to induce a quadrupole pattern in the final maps that is very similar to the officially published quadrupole mode. It is clear that a timing offset at the map-making stage will strongly affect the quadrupole scale, since the map-making in [The origin of the WMAP quadrupole, Hao Liu, Shao-Lin Xiong, Ti-Pei Li] was based on the official WMAP calibrated TOD. But there is also a possibility that the calibration process itself could be affected as well and we test this here. In this work we approximately reproduce the original dipole-based iterative calibration procedure to produce a calibrated data set starting from raw uncalibrated data. Using the calibrated data we generate a set of sky maps that we compare to the officially released maps and note some differences between our and official results. We also investigate the effects of various timing offsets introduced in the calibration stage on the final products. We find that a timing offset in the calibration process has little effect on the calibrated data and induced quadrupole.